slow graphics in cvi

[Niranjan]

Hi,
I am using cvi/labwindows for analog data acquisition from a board. I am acquring data and once the buffer is full i plot it using Plowaveform function. And while plotting is done, board continues to acquire data. basically i am using half buffering. i faced a strange problem when i run my program on few of the machine in our lab. On some machines, when i start acquiring data from multiple channels, the plotting of data slows down. this is unabling us to view the acquired data. When plotting reaches start of graph control, it plots fast with normal speed, but slows down as it continues to plot further. If I reduce size of graph control to a ridiculous size then it works fine. also same program works fine on some machines. One more thing is this ha
ppens only when i acquire data from more than 2 channels. i checked RAM, it is same for all machines. even i tried changing video card for one machine. however, it didn't help.
has anybody of u have faced such problem before?

cheers
niranjan

[DanielMcchane]

I think that you have several issues you can look into here. With the PlotWaveform function, you are displaying your data to a graph, which plots all points in one action. A way around this is to switch the graph control to a stripchart control. This will plot point at a time, and may reduce load on the processor.
Another option that you have is to use multithreading. This allows you to "split" processor time, and can allow you to aquire data while plotting at the same time. If you want more information on this topic, there is a MultithreadingOverview.pdf readme file that is located in the following folder of Measurement Studio 6.0:
C:\Program Files\National Instruments\MeasurementStudio\CVI\bin

Daniel McChane
Application Engineering
National Instr
uments

[Niranjan]

Thanks Daniel.